Chromium modified manganese ferrite oxidative dehydrogenation catalysts

ABSTRACT

The presence of 0.05 to 0.4 atom of chromium per atom of manganese in a manganese ferrite oxidative dehydrogenation catalyst improves the yields from oxidative dehydrogenation reactions employing such catalyst. A chromium modified manganese ferrite catalysts containing from 1 to 20 weight percent carbon is also disclosed.

United States. Patent 1191 Manning Jan. 7, 1975 CHROMIUM MODIFIED-MANGANESE 3,670,042 1 6/1972 Croce 6161 2607680 B FERRITE OXIDATIVE 3,686,347 8/1972 Dean et al.... 260/680 E 3,751,385 8/1973 Manning 260/680 E DEHYDROGENATION CATALYSTS 3,751,512 8/1973 Woskow et al 260/680 E Inventor: Harold E. Manning, Houston, Tex.

Petro-Tex Chemical Corporation, Houston, Tex.

Filed: Sept. 14,1972

Appl. No.: 289,177

Related US. Application Data Continuation-impart 0f Ser.. NO. 73,956, OCL 7, 1970, Pat. N0. 3,751,385.

Assignee:

References Cited UNITED STATES PATENTS 5/l972 Croce ct al 260/680 E Primary Examiner-Paul M. Coughlan, Jr. Attorney, Agent, or FirmN. Elton Dry [57] ABSTRACT The presence of 0.05 to 0.4 atom of chromium per atom of manganese in a manganese ferrite oxidative dehydrogenation catalyst improves. the yields from oxidative dehydrogenation reactions employing such catalyst A chromium modified manganese ferrite catalysts containing from 1 to 20 weight percent carbon is also disclosed.

3 Claims, No Drawings CHROMIUM ,MODIFIEUMANGANESE FERRIT OXIDATIVE DEHYDROGENATION CATALYSTS This application is a continuation-impart of co- .pending application Ser. No. 78,956 filed on Oct. 7,

1970 now U.S. Patent,3,75l,385 and the entire contents thereof are incorporated herein by reference.

This invention relatesto oxidative dehydrogenation of organic compounds having a least one grouping. More particularly the invention relates to the use of manganese ferrite catalyst in such oxidative dehydrogenation. Specifically the invention relates to manganese ferrite catalysts containing from 0.05 to 0.4

' atom of chromium per atom of manganese.

genated compounds. These non-selective reactions areparticularly evident when the compound to be dehydrogenated contains three or more carbon atoms. For example, when methyl butene is reacted with oxygen, avariety of products other than isoprene are possible as hydrocarbons and oxygenated hydrocarbons of various general mixtures may result; Also, combustion of the hydrocarbon may result in the formation of C0, C and water.

It is therefore one of the principal objectives of this invention to provide a process and catalyst wherein the organic compound is dehydrogenatedpreferably to a.

product having the same number of carbon atoms at a high level of conversion and selectivity. Another principal objective is to provide a process wherein the catalyst has long catalyst life. Other objectives of this invention are to provide a process wherein it is possible to have substantial quantities of steampresent in the dehydrogenation zone, a high over-all throughput and a low contact time in the dehydrogenation zone and a process which has good, control of reaction temperature. These andother objectives may be achieved by the process of this invention.

Briefly stated, one aspect of the present invention is an oxidative dehydrogenation catalyst comprising a manganese ferrite containing a minor amount of chromium. Generally the manganese ferrite will contain from about 0.05 to 0.4atom of chromium per atom of manganese contained in the catalyst and preferably about 0.05 to 0.2 atom of chromium per atom of manganese. In another embodiment of the present invention, the catalyst comprises manganese ferrite, 0.05 to 0.5 atoms of chromium per atom of manganese and about 1 to weight percent carbon black. In a preferred embodiment, the carbon black is present in a range of about 1 to 15 weight percentand more preferably about 2 to 10 weight percent.

In addition to chromium and carbon black the earthlyst may also contain binding agents or fillers, but'the chromium, carbon black and the binders and fillers will not ordinarily exceed about 50 percent or 60 percent by weight of the catalysts and the described catalytic compositions will preferably constitute the main active constituent. These binding agents and fillers will preferably be essentially inert. Preferred catalysts are those that have at least 25 or preferably 50 weight percentof the defined catalyst actives. Also preferably iron will constitute at least 50 atomic weight percent of the cations in the catalyst. Unless stated otherwise, the compositions in this application are the main active constituents of the dehydrogenation process during dehydrogenation and any ratios and percentages refer tov the surface of the catalyst in contact with the gaseous phase during dehydrogenation.

.The catalysts of this invention comprise manganese ferrite produced in a particular manner. Manganese ferrite comprises a complex crystalline structure cominventionsuperior catalystscan be formed by producing the manganese ferrite by reacting an active com pound of iron with an active compound of manganese. By active compound is meant a compound which is reactive under the conditions to form the ferrite;

The starting materials may be such as oxides, hydroxides, or salts including oxalates, acetates,'formates, sill fates, nitrates, halides, hydrates, and so forth. Suitable manganese compounds are such as manganese oxalate, manganese hydroxide, manganese nitrate, manganese carbonate, manganese salts of aliphatic monocarboxylic acids of l' to 5 carbon atoms, manganese sulfates, salts of aliphatic alcohols'ofl to 5 carbon atoms, hydrates thereof and mixtures thereof. The same classes of iron compounds may be employed such as iron nitrate, etc. The inorganic salts give excellent results.

The iron and manganese precursor components and the chromium containing component can be combined in any conventional manner which will provide an intimate mixture, for example, manganese oxide, iron oxide and chromium component can be mixed in a slurry or dry mixed. One component can be deposited on another or the precursor components, can be coprecipitated. I

One procedure for forming the catalysts is to prepare an aqueous mixture of the precursor salts and thereafter this mixture can then be precipitated by mixing with a basic reactant to precipitate the precursor of the ferrite. Any suitable base may be employed but those containing unwantedcatioris will, of course, be less desirable. Volatile bases such as ammonium hydroxide or carbonate may be employed.

The temperature used for ferrite formation may be varied, depending somewhat upon the particular starting materials and upon the conditions present during rate of heating of the reactants to form the ferrite. Here again the rate of heating will be dependent upon the particular reactants and conditions employed, but bet- I con halides, etc.

terresults are generally obtained when the reactants are heated at a rate of no greater than about 250 C per minute and still better results are ordinarily obtained when the rate is no greater than about 100 C per minute.

The ferrites are preferably prepared in an atmosphere containing little or no oxygenrPreferably the atmosphere will contain less oxygen than air, i.e., less than about mole percent oxygen. More preferably the calcining atmosphere will be substantially free of oxygen. Suitable atmospheres are gases such as nitrogen, helium, argon, neon, krypton, xenon and the like or mixtures thereof.

Improved manganese ferrite compositions may be obtained by utilizing halogen or halogen compounds during the formation of the ferrite. The use of halogen or halogen compounds in this manner is claimed in U.S.

Pat. No. 3,567,793, issued Mar. 2, 1971. An example of the use of a halogen would be the addition of manganese chloride to the reactants prior to' the formation of the ferrite. Normally, chlorine is the preferred halogen so used. Y a

The manganese ferrite compositions of this invention ,mayalso comprise additives. Phosphorus, silicon or mixtures thereof-are examples of additives. For ..in-

stance, phosphorus and/or silicon may suitably be present in an amount of from 0.2to 20 percent based on the total weight of the atoms of iron and manganese. These ingredients may contribute e.g. to the stability of the compositions. The silicon, phosphorus or other addi tives may be addedat various stages of the preparation of the composition, or may be added to the already formed manganese ferrite. Any suitable compounds may be employed such as phosphoric acid, phosphorus pentoxide, ethyl phosphate, ammonium phosphate, sili- The chromium is incorporated into ferrite preferably by combining a reactive chromium compound with the reactive iron and manganese compounds prior to react-- ing;to form the, ferrite. Suitable reactive materials are chromium oxide, chromium oxalate, chromium acetate, chromium sulfate and the like, as previously described for the iron and manganese starting material.

reflection peaks which are relatively broad. The degree of sharpness of the reflection peak may be measured by the reflection peak band width at half height (W h/2). in other words, the width of the reflection peak as measured at one-half of the distance to the top of the peak is the band width at half height. The band width at 7 half height is measured in units of 2 theta. Techniques for measuring the band widths are discussed, e.g., in-

Chapter 9 of Klug and Alexander, X-rayDiffraction ative thereof. Such'compounds normally will contain from 2 to 20 carbon atoms, at least one compounds may contain other elements, in addition to carbon and hydrogen such as oxygen, halogens, nitro-. I gen and sulphur. Preferred are compounds'having from 3 to 12 carbon atoms, and especially preferred are compounds of 3 to 6or 8 carbon atoms.

Among the types of organic compounds which may be successfully dehydrogenated to the corresponding unsaturated derivative by means of the novel process'of this-invention are nitriles, amines, 'alkyl'halides, ethers,

esters, aldehydes, 'ketones, alcohols, acids, alkyl aromatic compounds, alkyl heterocyclic compounds, cy-' cloalkanes, alkanes, alkenes, and the like. Illustration of dehydrogenations,includepropionitrile to acrylonitrile propionaldehyde to acrolein, ethyl chloride'to vinyl chloride, methyl isobutyrate' to methyl methacrylate, 2 or 3 chlorobutene-'1 or 2, 3-dichlorobutane to chloroprene; ethyl pyridine, to vinyl pyridine, ethylbenzene tostyrene, isopropylbenzene to a-methyl styrene, ethylcyclohexane to styrene, cyclohexane to benzene,

propane to propylene, isobutane to isobutyl'ene, nbutane to butene'and butadiene-l ,3, butene to butadiene-l ,3 and vinyl acetylene, methyl butene to isoprene,

The chromium modified manganese ferrite compositions may be reduced with a reducing gas prior to use in the process of dehydrogenation. Examples of reducing gases are hydrogen or hydrocarbons. For example, the manganese ferrite compositions may be reduced with e.g. hydrogen at a temperature of at least 250 C with the temperature of reduction generally being no greater than 850 C. By reducing gas is meant a gas that will react with oxygen under the conditions of reduction. However, it is one of the advantages ofthis inventain type of X-ray diffraction pattern. The preferred compositions do not have as sharp X-ray diffraction reflection peaks as would be found, e.g., in a high crystalline material having the same chemical composition. Instead, the preferred catalystof this invention exhibit cyclopentane, to cyclopentene and cyclopentadiene- 1,3, n-octane to ethyl benzene and ortho-xylene, monomethylheptanes to xylenes, propane to propylene to benzene, ethyl acetate to vinyl acetate, 2,4,4- trimethylpentane to xylenes, and the like. This invention may be useful for the formation of new carbon to carbon'bonds by theremoval of hydrogen atoms such as the formation of a carbocylic compound from two aliphatic hydrocarbon compounds or the formation of a dicyclic compound from amonocyclic compound having an acyclic group. Examples of conversions are the conversion of n-heptane to toluene and propene to diallyl. Representative materialswhich are dehydrogenated by the novel process of this invention include ethyl toluene, alkyl chlorobenzenes', ethyl naphthalene,

isobutyronitrile, propyl chloride, isobutyl chloride, ethylfluoride, ethylbromide, n-pentyl iodide, ethyl div chloride, 2,3-dichlorobutane, 1,3-dichlorobutane, l,4-'

dichlorobutane, the chlorofluoroethanes, methyl pentane, methylethyl ketone, diethylketone, n-butyl alcohol, methyl propionate, and the like. This invention is particularly adapted to the preparation of vinylidene compounds containing at least one CH C group, that is, a group containing a terminal methylene group attached by a double bond to a carbon atom, and having 2 to 12 carbon atoms by the dehydrogenation of compounds of the formula CH -CH R wherein R is an organic radical of from 0 to carbon atoms, preferably a hydrocarbon. Similarly, acetylenic compounds of the formula CH i! C- may be produced from the same starting materials.

Preferably oxygen is employed, suitably in an amount within the range of 0.2 to about 5.0 mols of oxygen per mol of organic compound to be dehydrogenated, preferably from 0.2 to 2.5 moles per mole. Generally, better results may be obtained if the oxygen concentration is maintained between about0l25 and about 1.6 moles of oxygen per mole of organic compound to be dehydrogenated, such as between 0.35 and 1.2 moles of oxygen. The oxygen may be fed to the reactor as pure oxygen, as air, as oxygen-enriched air, oxygen mixed with diluents, and so forth. Based on the total gaseous mixture entering the reactor, good results are obtained withoxygen present in an amount from about 0.5 to 25 volume percent of .the total gaseous mixture, such as in an amount from about 1 to volume percent of the total. The total amount of oxygen utilized may be introduced into the gaseous mixture entering the catalytic zone or sometimesit hasbeen found desirable to add the oxygen in increments, such as to differenct sections of the reactor. The above described proportions of oxygen employed are based on the total amount of oxygen used. The oxygen may be added directly to the reactor or it may be premixed, for example, with a diluent or steam. It is also within the scope of this invention to employ the described manganese compositions as the being particularly preferred. When terms such as halogen liberating materials or halogen materialsare used in the specification and claims, this includes anysource of halogen such as elemental halogens, hydrogen halides, or ammonium halides. The amount of halogen, calculated as elemental halogen, may be as little as about 0.0001 or less mole of halogen per mole of the organic compound to be dehydrogenated to as high as 0.2 or 0.5. The preferred range is from about 0.001 to 0.09 mole of halogen per-mole of the organic compound to be dehydrogenated.

The temperature for the dehydrogenation reaction generally will be at least about 250 C, such as greater than about 300 C or 375 C, and the maximum temperature in the reactor may be about 650 C or 750 C or perhaps higher such as 900 C under certain circum stances. However, excellent results are obtained within the range of or about 300 C to 575 C, such as from or about 325 C to about 525 C. The temperatures are measured at the maximum temperature in the dehydrogenation zone. An advantage of this invention is that lower temperatures of dehydrogenation may be utilized than are possible in conventional dehydrogenation pro tem will normally be about or in excess of atmospheric partial or sole source of oxygen used for oxidative dehydrogenation. For example, the manganese compositions may release oxygen to react with the organic compound during a dehydrogenation step and thereafter the manganese composition is regenerated by oxidation prior to another step where oxygen is released. Preferably such a process will have the manganese composition present as a moving bed.

It is one of the advantages of this invention that halogen may also be added to the reaction gases to give excellent results. The addition of halogen tothe feed is particularly effective when the hydrocarbon to be dehydrogenated is saturated. The halogen present in the dehydrogenation zone may be either elemental halogen or any compound of halogen which would liberate halogen under the conditions of reaction. Suitable sources of halogen are such as hydrogen iodide, hydrogen bromide and hydrogen chloride; aliphatic halides, such as ethyl iodide, methyl bromide, "1,2-dibromo ethane,

ethyl bromide, amyl bromide, and allyl bromide; cycloaliphatic halides, such as cyclohexylbromide; aromatic halides, such as benzyl bromide; halohydrins, such as ethylene bromohydrin; halogen substituted aliphatic acids, such as bromo-acetic acid; ammonium iodide;

pressure, although sub-atmospheric pressure may also desirably be used. Generally, the total pressure will be between about 4 p.s.i.a. and about or p.s.i.a. Preferably, the total pressure will be less than about 75 p.s.i.a. and excellent results are obtained at about atmospheric pressure.

Preferably, the reaction mixture contains a quantity of steam, with the range generally being between about 2 and 40 moles of steam per mole of organic compound to be dehydrogenated. Preferably, steam will be present in an amount from about 3 to 35 moles per mole of organic compound to be dehydrogenated and excellent results have been obtained within the range of about 5 to about 30 moles of steam per mole of organic compound to be dehydrogenated. The functions of the steam are several-fold, and the steam may not merely act as a diluent. Diluents generally may be used in the same quantities as specified for the steam.

The gaseous reactants may be conducted through the reaction chamber at a fairly wide range of flow rates. The optimum flow rate will be dependent upon such variables as the temperature of reaction, pressure, particle size, and whether a fluid bed or fixed bed reactor is utilized. Desirable flowrates may be established by one skilled in the art. Generally, the flow rates will be within the range of about 0.10 to 25 liquid volumes of the-organic compound'to be dehydrogenated per volume of dehydrogenation zone containing catalyst per hour (referred to as LHSV), wherein the volumes of void space is the volume of reactor containing catalyst for the purpose of calculating the flow rate. The gaseous hourly space velocity (GHSV) is the volume of the organic compound to be dehydrogenated in the form of vapor calculated under standard conditions of C and 760 mm of mercury per volume of reactor space containing catalyst per hour. Generally, the GHSV will be betweenabout 25 and 6400, and excellent results have been obtained between about 38 and 3800. Suitable contact times are, for example, from about 0.001 or higher to about 4 or or 25 seconds, with particularly good results being obtained between 0.01 and 5 seconds. The contact time is the calculated dwell time of the reaction mixture in the reaction mixture in the reaction zone, assuming the moles of product mixture are equivalent to the moles of feed mixture. For the purpose of calculation of contact times, the reaction zone isthe portion of the reactor containing catalyst which is at a temperature of at lease 250 C.

The dehydrogenation reactor may be of the fixed bed or fluid bed type. Conventional reactors for the production of unsaturated organic compounds by dehydrogenation are satisfactory. Excellent results have been obtained by packing the reactor with catalyst pars 100 vols. of N /vol. of catalyst/hour) to the final calcination temperature of 600 C and held at this temperature for 1 hour.

"baker Analyzed Reagent Grade 7 *Balcer (C.P.)

. Portions of catalyst A, B, C, and D were each calcined ticles as the method of introducing the catalytic surface. The catalytic surface may be introduced as such or it may be deposited on a carrier by methods known in the art such as by preparing an aqueous solution or dispersion of a catalytic material and mixing the carrier with the solution or dispersion untilthe active ingredients are coated on the carrier. If a carrier is utilized, very useful carriers are silicon carbide, aluminum oxide, pumice, and the like. vOther known catalysts carriers may be' employed. When carriers are'used, the amount of catalyst on the carrier will suitably be between about 5 to 75 weight percentof the total weight of. the active catalytic material plus carrier. Anothermethod forintroducing the required surface is to utilize as a reactoria small diameter tube wherein the tube wall is catalytic or is coated with'catalytic material. Other methods mayibe utilized to introduce the catalytic surface such as by the use of rods, wires, mesh, or shreds,

lyzed immediately by vapor phase chromatography.

EXAMPLE 1 Catalyst Preparation The catalysts-were prepared from the quantities of starting materials described in Table I. The materials were slurried togetherin distilled water for minutes using a one gallon Waring blender. The slurry was dried in an oven at 100? C. The dried cake was screened to remove particles larger than 40 mesh and calcined in a Vycor combustion tube (using a N atmosphere at at 600 Cas indicated above. Portions of .each of the calcined products were prepared foruse by depositing 76 grams of the calcined product and 2.3 grams of 86% H PO onto l45 grams of HCl leached 6-9 mesh AMC alumina. X-ray scan indicatedthat a manganese ferrite. was the predominant material in each calcined product The same amount of each catalyst was employed for the runs in Example 2 in the reactoras described.

- mole ratio of steamlo /hydrocarbon of 30/0.9/1. In

Table II the catalysts, maximum temperatures and results for eachrun arereported. 1

, TABLE 11 Temp. lsoprene Mole Run Catalyst "F Max. Conversion/Selectivity/Yield l A 970 58 90 52 2 B 930 61 90 54.9 3 C 950 62 88 .54.5 4 D 990 63 86.6 54.6

0.05 to 0.4 atom of chromium per atom'of manganese.

2. The process according to-claim 1 wherein the manganese ferrite contains 0.05 to 0.2 atom of chromium drocarbon comprises isoamylene.

UNITED STATES PATENT OFFICE CETEFICATE OF CORECTIUN Patent No, 3, Dated January 7, Inventor(s) Harold E. Manning It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 5, line 26 reads "differenct" but should read different Col. 7, line 14 reads "reaction mixture" but should read reaction Zone Col. 7, line 18 reads lease" but should read least I Col. 8, line approx. 10, (Table, lines 1,2 and 4 under Materials), Patent Office has used instead of asterisks to denote footnotes.

Col. 8, line 16 reads "baker" but should read Baker Signed and gcaled tis fourth Day of May 1976 [SEAL] A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting 0117" Commissioner Hflah-IIIS and Trademarks 

1. A PROCES FOR THE OXIDATIVE DEHYDROGENATION OF C5, HYDROCARBONS IN VAPOR PHASE COMPRISING CONTACTING SAID HYDROCARBONS IN THE PRESENCE OF OXYGEN AT A TEMPERATURE OF GREATER THAN 250*C, WITH A CATALYST CONSISTING ESSENIALLY OF A MANGAESE FERRITE CONTAINING FROM 0.05 TO 0.4 ATOM OF CHROMIUM PER ATOM OF MANGANESE.
 2. The process according to claim 1 wherein the manganese ferrite contains 0.05 to 0.2 atom of chromium per atom of manganese.
 3. The process according to claim 1 wherein the hydrocarbon comprises isoamylene. 